2-channel vs 3-channel/5channel

I've been there and done that. For me it was a waste of time and money.
With excellent imagining speakers I don't miss a think when I do watch a movie.
To be honest though, with my good 2- channel system I find myself wanting to enjoy good music rather then watch a movie.

I have found 4.1 (no center) to be MUCH more enjoyable than 2.0 for movies. I have sold off my surround sound a few times and always regret it.

So anyway, to answer your question, a good surround sound system not only gets you tremendous added dimension on movies, but SACD and DVD-A's cab be astounding.

As long as you don't mind effects that should be coming from the back or sides not coming, then your 2 channel system should be fine. If you want the immersive effect, then go for the full system.

This is the wrong forum to ask the question on anyway, as most would probably want to go back to mono given a choice.